Most types of electrical equipment rely, for their safe and efficient performance, on an electrical circuit and the means to keep this circuit isolated from the surrounding materials and environment. Many types of equipment also have a magnetic circuit, which is linked to the electrical circuit by the laws described.
The main characteristics of the material of relevance for the electrical engineering are therefore those associated with the conductors for the electrical circuit, with the insulation system necessary to isolate this circuit and with the specialized steels and the permanent magnets used for the circuit magnetic.
Other properties, such as mechanical, thermal and chemical properties, are also relevant, but they are often important in specialized cases and their coverage is best left to other books that address these areas more generally. The scope of this chapter is restricted to the main types and characteristics of conductors, insulation systems and magnetic materials commonly used in plants and electrical equipment.